Electro-Optical and Dielectric Investigations of Antiferroelectric and Ferrielectric Smectic Phases

Dielectric and electro-optical properties of the various antiferroelectric and ferrielectric smectic phases of two compounds of the homologous series MHPnCBC (n = 8,9) have been investigated. MHP9CBC exhibits an unidentified chiral induced SmC subphase (denoted by SmC x *) and shows the phase sequence Cr - SmI A * - SmC A * - SmC γ * - SmC SmC x * - SmC SmC x * - SmA - I. The electro-optical and dielectric properties of the SmC SmC x * phase of MHP9CBC differ distinctly from that of the SmC SmC α * as well as the SmC SmC γ * phase. The electric field - temperature phase diagram was obtained by two methods, measurement of the apparent tilt angle as well as the dielectric loss. The results of both methods are in good agreement. For both compounds a field induced ferrielectric state is observed in a broad temperature range (≊ 10 K) of the SmC SmC A *−phase.